Gray-scale transformation of Qt image processing and qt gray-scale

Gray-scale transformation of Qt image processing and qt gray-scale

Changing the brightness and contrast of an image is a common image processing operation, but Qt itself does not provide the corresponding functional code. Therefore, I wrote a simple class to implement these operations. I call this class BrightnessMapper.

 

The Code is as follows:

#ifndef BRIGHTNESSMAPPER_H#define BRIGHTNESSMAPPER_H#include <QImage>class BrightnessMapper{public:    BrightnessMapper();    ~BrightnessMapper();    void setRedMap(unsigned char red[]);    void setGreenMap(unsigned char green[]);    void setBlueMap(unsigned char blue[]);    void setMap(unsigned char map[]);    void updateBCG(double brightness, double contrast, double gamma);    void setColorMap(unsigned char red[], unsigned char green[], unsigned char blue[]);    void apply(const QImage &from, QImage &to);    QImage apply(const QImage &from);    unsigned char *redMap(){ return m_red;}    unsigned char *blueMap(){return m_blue;}    unsigned char *greenMap(){return m_green;}    void redMap(double red[256]);    void greenMap(double green[256]);    void blueMap(double blue[256]);private:    unsigned char m_red[256];    unsigned char m_green[256];    unsigned char m_blue[256];};#endif // BRIGHTNESSMAPPER_H

#include "brightnessmapper.h"#include <math.h>#include <QDebug>BrightnessMapper::BrightnessMapper(){    for(int i = 0; i < 256; i++)    {        m_red[i] = i;        m_green[i] = i;        m_blue[i] = i;    }}BrightnessMapper::~BrightnessMapper(){}void BrightnessMapper::updateBCG(double brightness, double contrast, double gamma){    double x, y;    for(int i = 0; i < 256; i ++)    {        x = i / 255.0;        y = exp(log(x) * gamma);        y = (y - 0.5) * brightness + 0.5 + contrast / 255;        y = y * 255.0;        m_red[i] = qBound(0.0, y, 255.0);        m_green[i] = m_red[i];        m_blue[i] = m_red[i];    }}QImage BrightnessMapper::apply(const QImage &from){    QImage to = from;    apply(from, to);    return to;}void BrightnessMapper::apply(const QImage &from, QImage &to){    if(to.size() != from.size() || to.format()!= from.format())    {        to = from.copy();    }    int height = from.height();    int width = from.width();    switch(from.format())    {    case QImage::Format_Indexed8:        for(int i = 0; i < height; i++)        {            const uchar *pFrom = (const uchar *)from.constScanLine(i);            uchar *pTo = (uchar *)to.scanLine(i);            for(int j = 0; j < width; j++)            {                pTo[j] = m_red[pFrom[i]];            }        }        break;    case QImage::Format_RGB32:    case QImage::Format_ARGB32:    case QImage::Format_ARGB32_Premultiplied:        for(int i = 0; i < height; i++)        {            const QRgb *pFrom = (const QRgb *)from.constScanLine(i);            QRgb *pTo = (QRgb *)to.scanLine(i);            for(int j = 0; j < width; j++)            {                int r, g, b;                r = qRed(pFrom[j]);                g = qGreen(pFrom[j]);                b = qBlue(pFrom[j]);                r = m_red[r];                g = m_green[g];                b = m_blue[b];                pTo[j] = qRgb(r, g, b);            }        }        break;    }}void BrightnessMapper::setRedMap(unsigned char red[]){    for(int i = 0; i < 256; i++)    {        m_red[i] = red[i];    }}void BrightnessMapper::setGreenMap(unsigned char green[]){    for(int i = 0; i < 256; i++)    {        m_green[i] = green[i];    }}void BrightnessMapper::setBlueMap(unsigned char blue[]){    for(int i = 0; i < 256; i++)    {        m_blue[i] = blue[i];    }}void BrightnessMapper::setMap(unsigned char map[]){    for(int i = 0; i < 256; i++)    {        m_red[i] = map[i];        m_green[i] = map[i];        m_blue[i] = map[i];    }}void BrightnessMapper::setColorMap(unsigned char red[], unsigned char green[], unsigned char blue[]){    for(int i = 0; i < 256; i++)    {        m_red[i] = red[i];        m_green[i] = green[i];        m_blue[i] = blue[i];    }}void BrightnessMapper::redMap(double red[256]){    for(int i = 0; i < 256; i++)    {        red[i] = m_red[i];    }}void BrightnessMapper::greenMap(double green[256]){    for(int i = 0; i < 256; i++)    {        green[i] = m_green[i];    }}void BrightnessMapper::blueMap(double blue[256]){    for(int i = 0; i < 256; i++)    {        blue[i] = m_blue[i];    }}

This class is easy to use. You can use the following functions to set the gray-scale conversion relationship.

 

Void setRedMap (unsigned char red []);

Void setGreenMap (unsigned char green []);

Void setBlueMap (unsigned char blue []);

Void setMap (unsigned char map []);

Void setColorMap (unsigned char red [], unsigned char green [], unsigned char blue []);

 

You can also use the following function to determine the Conversion Relationship by setting the brightness, contrast, and gamma values.

Void updateBCG (double brightness, double contrast, double gamma );

 

After the conversion relationship is determined, you can use one of the following two functions to transform the image.

Void apply (const QImage & from, QImage & );

QImage apply (const QImage & from );

 

There are also several auxiliary functions that can be used to read the transformed relational table.

Unsigned char * redMap () {return m_red ;}

Unsigned char * blueMap () {return m_blue ;}

Unsigned char * greenMap () {return m_green ;}

Void redMap (double red [1, 256]);

Void greenMap (double green [1, 256]);

Void blueMap (double blue [256]);

 

Because the code is simple to answer, I will not introduce it much. I hope it will be useful to you.

 

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